Speed responsive warning switch



Aug. 5, 1958 w. H. FARR 2,846,539

SPEED RESPONSIVE WARNING SWITCH Filed Dec. 2, 1953 2 Sheets-Sheet 1 J r 7 M F 86 m4 56 Mm 20 4 2 410 k? l: 515% 90 94! I 4 4 i Aug. 5, 1958 v w. H. FARR 2,846,539

SPEED RESPONSIVE WARNING SWITCH Filed Dec. 2, 1953 2 Sheets-Sheet 2 United States Patent O SPEED RESPONSIVE WARNING SWITCH Willard H. Farr, Chicago, Ill., assignor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia Application December 2, 1953, Serial No. 395,665

6 Claims. (Cl. 200-80) The present invention relates to an improved speed responsive warning switch especially suited for use with an automotive vehicle engine to guard against overspeeding of the engine.

Even though an automotive vehicle is equipped with a tachometer for indicating engine speed, the operator may inadvertently overspeed the engine, particularly in the lower gears. To guard against this an audible or visible warning signal may be provided.

One object of the invention is to provide for controlling such a warning signal, an improved, dependable switch responsive to engine speed, which is well suited for economical manufacture on a mass production basis. A related object is to provide a switch which can be readily adjusted or calibrated to operate at different critical speeds.

Another object is to provide a warning switch of the above character which is adapted to be mounted in tandem with an internal combustion engine tachometer thus simplifying connection of the switch with the engine.

Other objects and advantages will appear from the following description of the form of the invention shown in the drawings, in which:

Figure 1 is a partially sectioned side view showing a switch embodying the invention connected to a warning signal and illustrating the mechanical connection of the switch between a tachometer and an engine driven drive therefor;

Fig. 2 is a longitudinal sectional view taken generally along the line 2-2 of Fig. 1;

Fig. 3 is a transverse sectional view taken along the line 3-3 of Fig. 2; and

Fig. 4 is a transverse sectional view taken along the line 44 of Fig. 2.

As shown in Fig. 1, the speed responsive warning switch incorporating the invention is coupled between a tachometer and a rotary drive 12 from a vehicle engine (not shown). An internally threaded coupling sleeve 14 adapted for connection with the drive 12 is mounted in the central end portion of a cupped casing member 16. The upon end of the casing member 16 is covered by a plate 18. The peripheral edge of the plate is turned around an annular gasket 19 and a radial flange 20 on the casing member to hold the plate in place. A second coupling sleeve 22 mounted on the central portion of the plate 18 in alignment with the sleeve 14 is externally threaded to connect with a mounting boss 24 on the tachometer 10.

The two coupling sleeves 14, 22 support needle bearings 26, 28 which journal opposite ends of a coupling shaft 30 extending through the casing 32 formed by the member 16 and the plate 18. A seal 34 centrally mounted in the sleeve 14 encircles the adjacent outer end of the shaft 30. This end of the shaft is suitably fashioned for connection with a rotary driving element (not shown) of the conventional drive 12. The opposite end of the ice shaft 30 is fashioned for connection with a rotary element of the tachometer 10.

A support spool 36, pinned to the shaft 30 within the casing 32, abuts against a thrust washer 38 interposed between the outer end of the spool and the inner end of the sleeve 14. The inner end of the spool, which extends to the medial portion of the casing 32, drives a support web 40 for three bell crank control weights 41.

The web 40 is fashioned from two centrally apertured, sheet metal discs 42, 44 formed substantially as mirror images of each other. The discs are riveted together and fixed on the necked down inner end of the spool 36.

Each of the bell crank weights 41 comprises a sheet metal stamping 48 having an actuator leg 50 and a weighted leg 52 running from a substantially right angled apex 54. The mass of the weighted leg of each weight is increased by two circular weights 56 pinned on opposite sides of an enlargement 58 on the leg running generally in the same direction as the actuator leg 50 of the weight. A pivot pin 60 is inserted perpendicularly through the apex 54 of each weight to protrude beyond opposite sides of the stamping 48.

The three weights are swingably mounted on the web 40 in circumferentially spaced relation about the spool 36. The pivot pin 60 of each weight is mounted in a receiver 62 formed between the web discs 42, 44 near the spool 36 by opposed, elongated indentations 64 struck in the mating faces of the discs. The actuator legs 50 of the weights swing through three radial slots 66 formed in the web 40 and extending through the medial portions of the respective receivers 62. The weighted legs 52 run along the spool 36.

The weighted legs 52 of the control weights 41 are biased toward the spool 36 by a triangular arrangement of three tension springs 68 hooked at opposite ends into apertures 70 formed in the outer ends of the adjacent legs (see Figs. 2 and 3). The central portion of each spring 68 extends through a radially relieved section 72 on the adjacent outer end of the spool 36. Inward movement of each weighted leg 52 is limited by engagement of a short medial projection 74 on the leg with the spool 36.

The outer ends of the actuator legs 50 project through the web slots 66 to engage a follower disc 76 of insulating material fixed to a sleeve 78 slidably mounted on the shaft 30 on the side of the web 40 opposite from the weighted legs 52. The follower disc 76 is urged toward the control weights 41 by a compression spring 80 encircling the sleeve 78 between a shoulder 82 on the sleeve and a washer 84 fixed to the shaft by a snap ring 86. A thrust washer 88 is interposed between the other side of the snap ring 86 and the inner end of the sleeve 22.

An adjustable electrical contact assembly 90 is mounted on the inner face of the cover plate 18 to be operated by the follower disc '76. The assembly 90 comprises a transverse contact plate 92 swingably supported at one end on an L-shaped bracket 94 fixed to the inner face of the casing plate 18. Three prongs 93 on the bracket 94 extend through notches in the plate. The plate is prevented from sliding off the prongs by a speed nut 97 on the outer end of the central prong. From the bracket 94, the plate 92 extends transversely across the casing 32. The sleeve 78 and the spring 80 extend through a central hole 95 in the plate.

The opposite end of the plate 92 is held in adjustable spaced relation to the casing plate 18 by an adjusting screw 96 extending through the casing plate and threaded into a U-shaped retainer 98 anchored in a rectangular opening 99 in the contact plate. The screw 96 acts in opposition to a conical compression spring 100 encircling the screw between the casing plate and the contact plate.

One electrical contact 102 of the switch is fixed to the inner face of the contact plate 92 between the retainer 98 and the hole 95. The plate 92 is formed from an insulating material. The contact 102 is connected by a wire 104 with a terminal bolt 106 extending through the cover plate 18 and clamping two insulator plates 108 and 110 to opposite sides of the cover plate.

A second switching contact 111 is mounted on the free end of a flexible contact support member 112 in opposed spaced relation to the contact 102. Formed of a thin centrally open sheet of spring metal, the support member 112 extends along the inner face of the plate 92 from the contact 111 to the opposite side of the sleeve 78.

The end of the sheet 112 adjacent the bracket 94 is fixed to the contact plate 92 by two laterally spaced rivets 114 and spaced therefrom by thick washers 116.

The movable contact 111 makes an electrical connection with its flexible support 112. An ear 120 on the mounted end of the support 112 (Fig. 4) is connected by a wire 122 with a second terminal bolt 124 disposed on the side of the sleeve 22 opposite from the terminal bolt 106. The bolt 124 extends outwardly through the insulator plate 110, an insulating washer 126 in the casing plate 18, and the insulator plate 108.

Two nylon actuator buttons 128 are mounted on the medial section of the flexible contact support 112 on opposite sides of the sleeve 78. Each actuator button 128 is held against the side of the support 112 opposing the follower 76 by a speed nut 130 fixed to a small central projection 132 on the button which extends through the support.

The terminal 106 is grounded by a wire 133. The other terminal 124 is connected by a wire 134 to a suitable visual or audible signal device 136 connected in series with the vehicle battery 138 and mounted on the vehicle to give an unmistakable warning to the operator.

To briefly review the operation of the speed responsive switch thus provided, it will be appreciated that upon rotation of the support web 40 by the coupling shaft 30, the control weights 41 will be turned about their pivotal supports by centrifugal forces acting against the springs 68. The actuator legs 50 of the control weights displace the follower disc 76 toward the contact assembly 90 a distance varying with the speed of rotation of the shaft 30. As the shaft speed increases the follower disc 76 engages the actuator buttons 128 forcing the switch contact 111 toward the contact 102.

When the speed of the shaft 30 has reached a predetermined critical value, the contact 111 will be engaged with the contact 102. This closes the circuit through the signal 136 to warn the operator that the vehicle engine speed is excessive.

As the speed of the shaft 30 drops back below this critical value, the movement of the follower disc 76 is reversed permitting the flexible support 112 to disengage the contact 111 from the contact 102, thus opening the circuit to the signal 136.

The position of the contact plate 92 and the contact support 112 in relation to the web 40, can be adjusted by turning the adjusting screw 96. This adjustment varies the degree of movement of the follower disc 76 along the shaft 30 necessary to close the switch contacts, which in turn determines the critical speed of the shaft at which the switch will be opened and closed.

Composed of simple, easily fabricated parts, the switch is well suited for economical manufacture on a mass production basis. The capability of the switch to serve as a driving coupling between a tachometer and a drive 12 simplifies its installation on a vehicle.

While I have shown and described a preferred embodiment of my invention, it will be apparent that variations and modifications thereof may be made without departing from the principles and scope of the invention. 1 therefore desire, by the following claims, to include all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. A speed responsive warning switch adapted to be used as a coupling in a rotary tachometer drive or the like and comprising, in combination, a generally circular casing, two coupling elements in opposite ends of said casing, each of said coupling elements defining a shaft opening extending therethrough and opening outwardly from said casing in axial alignment with a similar opening in the other coupling element, each of said coupling elements including a shaft support bearing aligned with said opening therein, a coupling shaft extending through said casing and journaled at opposite ends in said bearings of said respective coupling elements, opposite ends of said shaft being exposed through said respective coupling element openings for coupling, a rotary web mounted on said shaft for rotation therewith within said casing, a plurality of centrifugal weights, means pivotally mounting said respective weights on said web, each of said weights being shaped to have a center of gravity radially spaced from said pivotal mounting means therefor and to form on the weight an actuating element swingable longitudinally along said shaft as an incident to pivoting of the weight by centrifugal force acting through the center of gravity thereof, a follower encircling said shaft for movement longitudinally therealong in opposing relation to said actuating elements, a spring mounted to urge the follower in a direction for engagement by said actuating elements, a contact plate movably supported within said casing, adjusting means coacting with said contact plate to adjust the position of the latter toward and away from said follower, a first switching contact mounted on said plate, a movable support member mounted on said plate, a second switching contact mounted on said support member in separable coacting relation to said first contact, and actuating means on said support member engageable by said follower for controlling mutual engagement of said switching contacts in accordance with the pivotal positions of said weights.

2. A speed responsive warning switch comprising, in combination, a casing. a rotary shaft extending through said casing and journaled in opposite ends thereof, a support web mounted on said shaft within said casing. a plurality of bell crank Weights pivotally mounted on said web, each of said weights including a weighted leg extending generally along said shaft and an actuator leg extending radially outward from the pivotal support for the weight, a follower member encircling said shaft on the side of said web opposite from said weighted legs, a spring urging said follower member toward said web, a contact plate swingably mounted within said casing on the side of said follower member opposite from said web, threaded adjusting means for controllably shifting the position of said contact plate along said shaft, a first switching contact mounted on said plate and connected to a terminal on said casing, a flexible contact support mounted on said plate, a second switching contact mounted on said flexible support and connected with a second terminal on said casing, and an actuating member on said flexible contact support positioned for operation by said follower member upon movement of the latter away from said web by said weights.

3. A speed responsive switch comprising, in combination, a casing, a rotary drive member journaled in said casing, speed responsive weight means mounted for rotation by said drive member, a plate swingably mounted toward one end thereof within said casing about an axis perpendicular to said rotary drive member, threaded adjusting means connected with said plate near the opposite end thereof for moving the latter in one direction, a spring mounted to urge said plate in the opposite direction, a resilient contact support mounted on said plate, a first switching contact mounted on said support, a second contact mounted on said plate in opposed relation to said first contact, and means coacting with said weight means for closing said contacts as an incident to rotation of said drive member at a critical speed determined by the position of said plate.

4. A speed responsive warning switch comprising, in combination, a casing, a shaft journaled in said casing, a support web mounted on said shaft for rotation therewith, said web including a pair of generally flat discs formed substantially as mirror images of each other and held in face to face mutual engagement, a plurality of circumferentially spaced receivers formed in said web by opposed indentations in said discs thereof, a plurality of centrifugal weights pivotally supported on said Web by pivot pins disposed in said respective receivers, spring means connected with said weights to urge the latter in a direction for moving their centers of gravity inwardly, and switching means mounted within said casing for operation by said centrifugal weights as an incident to rotation of said shaft at a critical predetermined speed.'

5. A speed responsive control switch adapted to serve as a coupling between a tachometer and a rotary drive therefor and comprising, in combination, a casing including a cupped casing member and a plate covering the open end of said cupped member, a pair of electrical terminals mounted in said cover plate, a first coupling sleeve mounted in said cover plate and opening outwardly from said casing, a second coupling sleeve mounted substantially in the center of said casing member in alignment with said first sleeve and opening outwardly from said casing, a coupling shaft extending through said casing and journaled in said sleeves, opposite ends of said shaft being exposed and adapted for connection to rotary drive structure a web mounted on said shaft for rotation therewith, a plurality of bell crank weights pivoted on said web, each of said weights having an actuator leg and a weighted leg, spring means connected to said weights to bias said weighted legs thereof inwardly, a follower disc encircling said shaft, spring means biasing said disc toward said web for actuation by said weights,

a contact plate swingably mounted within said casing on the side of said follower disc opposite from said web, screw means for adjusting the position of said plate along said shaft, a resilient contact support mounted on said plate, a first switching contact mounted on said support and a second switching contact mounted on said plate, and means on said support engageable with said follower disc to close said contacts.

6. A speed responsive warning switch adapted to be mounted in tandem with a tachometer and comprising, in combination, a casing, a shaft journaled in said casing, a spool fixed to said shaft within said casing, a pair of discs formed generally as mirror images of each other and mounted on said spool in mutual engagement to form a support web, a plurality of bell crank centrifugal weights each having a pivot pin extending through the apex thereof, said weights being mounted on said web with said pins therefor disposed in circumferentially spaced receivers formed between said discs, each of said weights having a weighted leg extending along said spool and an actuator leg extending radially away from the pivotal support for the weight, spring means connected to said Weights to urge said weighted legs thereof toward said spool, a follower member mounted on a sleeve slidable on said shaft on the side of said support web opposite from said weighted legs, spring means urging said follower member toward said web to engage said actuator legs, and a switching assembly mounted in said cas ing for actuation by said follower member.

References Cited in the file of this patent UNITED STATES PATENTS 2,331,442 Trible Oct. 12, 1943 2,484,781 Cofiey Oct. 11, 1949 2,606,753 Bone Aug. 12, 1952 2,628,294 Bone Feb. 10, 1953 2,673,907 Purdy Mar. 30, 1954 2,703,831 Covington Mar. 8, 1955 2,758,172 Kromholz Aug. 7, 1956 

